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Old 26 November 2013, 06:23   #1
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Use of stainless steel bolts throughout the towning train.

I`m in the process of giving my Defender a bit of a "facelift" and I`ve removed the winch bumper and adjustable tow hitch for shot blasting and dipping. I`m just about to replace all the various tow-balls, as well as the usual one at the rear I`ve fitted a front bumper mounted hitch for easier handling of the trailer.
I`ve also purchased on Ebay a replacement front bumper bolt kit c/w stainless steel M10 bolts.
Does anyone have misgivings on the use of stainless steel in this application. I had intended to replace all fixings with stainless steel A4 grade wherever possible?
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Old 26 November 2013, 06:53   #2
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As an engineer working regularly on sea-going ships, I see SS nuts and bolts quite regularly. (They do all rust eventually, but SS take a lot longer than Mild Steel, depending on husbandry v neglect). I'd say there's nothing wrong with using them at all.

Just remember to put some copper grease (or similar) on the thread so you can undo it a little more easily in the future.

That said, I would imagine you'd need years of rust (and neglect) before the rust eats through a bolt of that size whether SS or MS.
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Old 26 November 2013, 08:20   #3
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Quote:
Originally Posted by Razorbill View Post
I`m in the process of giving my Defender a bit of a "facelift" and I`ve removed the winch bumper and adjustable tow hitch for shot blasting and dipping. I`m just about to replace all the various tow-balls, as well as the usual one at the rear I`ve fitted a front bumper mounted hitch for easier handling of the trailer.
I`ve also purchased on Ebay a replacement front bumper bolt kit c/w stainless steel M10 bolts.
Does anyone have misgivings on the use of stainless steel in this application. I had intended to replace all fixings with stainless steel A4 grade wherever possible?
Just be careful of fitting then in direct contact with unpainted aluminium or a galvanised surface....

Simon

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Old 26 November 2013, 08:24   #4
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I was told by an engineer not to use stainless bolts on a towbar as they were too brittle? Please correct me if I am wrong? Cheers
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Old 26 November 2013, 08:27   #5
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Not wrong They ain't as robust
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Old 26 November 2013, 08:29   #6
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Can't say I've heard of that one. Might have to go Google that now!
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Old 26 November 2013, 08:42   #7
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Only use high tensile bolts on towing applications. Another thing to watch for with stainless on stainless is if they stick together if they get hot.
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Old 26 November 2013, 09:02   #8
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Found this:

It is a common misconception that stainless steel is stronger than regular steel. In fact, due to the low carbon content, stainless steel cannot be hardened. Therefore when compared with regular steel it is slightly stronger than an un-hardened (grade 2) steel fastener but significantly weaker than hardened steel fasteners.

From this website: Bolt Depot - Selecting Fastener Materials - Steel Grades, Brass, Bronze, Stainless Steel

I did find other websites that all said pretty much the same. So potentially SS may be slightly weaker than hardened steel, but it also appears that the galvanised/aluminium to which it's fastened would break before either steel type.

You learn something every day!
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Old 26 November 2013, 11:51   #9
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Stainles is weaker for sure
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Old 26 November 2013, 12:50   #10
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"Stronger" isn't a useful description, fairly meaningless in describing metals or other materials. There are many different types of strength.

Stainless is much harder than carbon steel but as a consequence is also much more brittle.

For Dan's application, SS will probably be ok but at the same time shouldn't be used, especially when you consider the consequences of a failure.

High tensile bolts are the right ones for the job, stamped with 4.8 on the head rather than 8.8.

If you're worried about corrosion then hot dip galv'd rather than zinc plated will last a lot longer
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